Depending on which aspects of e4 interest you, check one or more of the following (note that source components only give you source):

e4 Resources: This will install a patch against the Eclipse Platform from the 3.5 stream, replacing the resources component with the e4 edition. The e4 version is fully backwards compatible, but contains a number of new capabilities. See the e4 New & Noteworthy document for details.

e4 SWT: This will install the ActionScript development environment which is used to generate cross-compiled SWT apps.

Installing an M2 Integration Build

Prep: Go to the integration builds page, navigate to the desired build (if you're not sure which to choose, use the stable build, 0.9M2 at the time of this writing), then look down in the bottom right corner for "online p2 repo link". Copy the underlying URL.

Select Help > Install New Software...

Click on the "Add Site..." button and paste the URL.

Follow the remaining instructions above in the section "Installing M1".

Installing an M3 Integration Build

Prep: Go to the integration builds page, navigate to the desired build (if you're not sure which to choose, use the latest stable build, 0.9M3 at the time of this writing), then look down in the bottom right corner for "online p2 repo link". Copy the underlying URL.

Select Help > Install New Software...

Click on the "Add Site..." button and paste the URL.

Follow the remaining instructions above in the section "Installing M1".

Demos

[1] Note that the Eclipse e4 UI work also requires the EMF runtime. This will be brought in automatically. However, if you wish to view or edit the UI model and you're not a fan of XML source editing, you will want to install the EMF SDK which provides the EMF .xmi editor. Follow "Help" -> "Install New Software..." -> "Models and Model Development" -> "EMF SDK - Eclipse Modeling Framework SDK 2.4.1 or 2.5.0", then restart Eclipse.